We
would like to let you know that, at present there is no event as
SelectedTabItemChanging. And how ever your requirement for disabling TabItem
selection navigation can be achieved by handling ToolstripTabItem Click
event.

Please
find the code snippet below for your reference:

Code
Snippet:[C#]

if (this.DisableTabNavigation)

this.ribbonControlAdv1.SelectedTab = this.PrevSelectedTab;

We
have also prepared sample that tries to meet your requirement and it can be
downloaded from below location: